title: Optimal flow rates for integrated cardioplegia.
abstract: BACKGROUND
  Antegrade cardioplegic delivery may be impaired by coronary occlusions, whereas retrograde delivery of cardioplegic solution may be inhomogeneous, leading to an accumulation of lactate and hydrogen ions, the products of anaerobic metabolism. Integrated cardioplegia using continuous retrograde cardioplegia and antegrade infusions into completed vein grafts washes out metabolites accumulated in regions inadequately perfused by retrograde cardioplegia alone. To determine the flow rates required to achieve the greatest washout, we compared a high flow rate (200 ml/min) to a low flow rate (100 ml/min).
  
  
  METHODS
  Twenty patients scheduled for isolated coronary bypass surgery were prospectively randomized to compare two flow rates for integrated cardioplegic protection using tepid (29 degrees C) blood cardioplegia. Arterial and coronary sinus blood samples were collected to evaluate myocardial metabolism. After antegrade arrest, cardioplegic solution was delivered by coronary sinus perfusion and simultaneous infusions into each completed vein graft at either high or low flow.
  
  
  RESULTS
  Increasing from low to high flow increased the washout of lactate and hydrogen ions during the aortic crossclamp period. Two hours after crossclamp removal, ventricular function was better in the high flow groups.
  
  
  CONCLUSIONS
  Tepid retrograde cardioplegia resulted in an accumulation of toxic metabolites. The addition of antegrade vein graft infusions at a flow rate of 100 ml/min resulted in a washout of these metabolites. A flow rate of 200 ml/min further improved this washout and resulted in improved ventricular function. An integrated approach to myocardial protection using a flow rate of 200 ml/min may improve the results of coronary bypass surgery.
authors.affiliation: Division of Cardiovascular Surgery, Toronto Hospital, Ontario, Canada.
authors.forename: V
authors.initials: V
authors.lastname: Rao
authors.forename: G
authors.initials: G
authors.lastname: Cohen
authors.forename: R D
authors.initials: RD
authors.lastname: Weisel
authors.forename: N
authors.initials: N
authors.lastname: Shiono
authors.forename: Y
authors.initials: Y
authors.lastname: Nonami
authors.forename: S M
authors.initials: SM
authors.lastname: Carson
authors.forename: J
authors.initials: J
authors.lastname: Ivanov
authors.forename: M A
authors.initials: MA
authors.lastname: Borger
authors.forename: R J
authors.initials: RJ
authors.lastname: Cusimano
authors.forename: D A
authors.initials: DA
authors.lastname: Mickle
mesh_terms: D001769:Blood; D002314:Cardioplegic Solutions / Q000008:administration & dosage*; D002315:Cardiopulmonary Bypass; D001026:Coronary Artery Bypass; D006324:Heart Arrest, Induced / Q000379:methods*; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism; D008875:Middle Aged; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control*; D009206:Myocardium / Q000378:metabolism; D010101:Oxygen Consumption; D011446:Prospective Studies; D011522:Protons
chemical_list: D002314:Cardioplegic Solutions; D011522:Protons; D019344:Lactic Acid